Eovlaldi has been on the 60-day disabled list since spring training due to shoulder inflammation.
Betancourt exited after throwing two pitches in the dirt. He doesn't believe his injury is serious, though it has bothered him for a month. He is scheduled to undergo an MRI Wednesday.
"We will see what will come from tomorrow. We have Thursday off, and I hope it will be fine if I don't pitch those two days. If it was more serious I would tell you. If it was really bad I would tell you. But it's getting tight every time, and it's not easy to pitch like that," Betancourt said.
Doumit, who played right field, slapped an RBI single in the eighth inning and finished 2 for 5 with an RBI in a 5-4 defeat. He is hitting .226 with three homers and 17 RBI in 124 at-bats.
Mesoraco hit a solo home run in the ninth inning, to add an insurance run, after walking in a run in the first inning. Mesoraco finished the game 1 for 3 with two RBI, one run scored and one walk. He is batting .234 in 77 at-bats.
Van Slyke struck out swinging for the final out of a 5-2 defeat. He is hitting 250 with three homers and four RBI.
Young went 2 for 4 in the game with a solo home run to left-center. He added a sacrifice groundout that brought in another run in the seventh inning, in a 7-3 win. He scored once and drove in two, his first multi-RBI game of the season.
Young is batting just .214 with a .685 on-base plus slugging percentage in 18 games since returning from ankle surgery.
Cain ran into trouble early on as he allowed a run-scoring doubles to both Ryan Zimmerman and Ian Desmond in the opening frame. He bounced back with six scoreless innings before his night was over. The right-hander yielded two runs, four hits and walked two over seven innings of work in a 4-2 win in extras.
Cain has allowed two runs ore fewer in each of his last three starts at home. He is scheduled to make his next start Monday at Oakland. He allowed one run and three hits over seven innings of work in his previous meeting against the A's in 2012.
Descalso raised his batting average to .228 on the season, while hitting his second home run. He has 12 RBI in 30 games.
Soriano entered the ninth inning of the game with a 2-1 lead and promptly allowed an infield single to let the tying run on base. He got the next two batters out and seemed to be on his way to the save, before allowing a game-tying triple to Gregor Blanco.
Soriano finished the inning without any more damage, but he blew his third save in 15 appearances. The Nationals would lose the game, 4-2, in 10 innings. Soriano has a 2.25 ERA in 20 innings of work.
Volquez (3-5) pitched two scoreless innings before surrendering a run-scoring double to Matt Carpenter in the third inning. He then gave up four runs in the fifth, including a two-run single to Carlos Beltran. The right-hander was charged with five runs on eight hits in six innings of work. He struck out five and walked one in a 10-2 defeat.
Volquez has allowed five runs in each of his last two starts. He is 0-2 with a 6.35 ERA in his last three starts since May 3, when he won his third consecutive start. He is scheduled to make his next start Monday at Seattle. Volquez went 2-0 with a 0.68 ERA in two starts against the Mariners last season.